-LRB- CNN -RRB- -- Little more than a year after he resigned in disgrace as prime minister , Silvio Berlusconi is campaigning to win his old job back -- for the fourth time .

Berlusconi , the septuagenarian playboy billionaire nicknamed `` Il Cavaliere , '' has been trailing in polls behind his center-left rival , Per Luigi Bersani .

But the controversial media tycoon 's rise in the polls in recent weeks , combined with widespread public disillusionment and the quirks of Italy 's complex electoral system , means that nothing about the race is a foregone conclusion .

Why have the elections been called now ?

Italian parliamentarians are elected for five-year terms , with the current one due to end in April . However in December , Berlusconi 's People of Freedom Party -LRB- PdL -RRB- withdrew its support from the reformist government led by Mario Monti , saying it was pursuing policies that `` were too German-centric . '' Monti subsequently resigned and the parliament was dissolved .

Berlusconi -- the country 's longest serving post-war leader -- had resigned the prime ministerial office himself amidst a parliamentary revolt in November 2011 . He left at a time of personal and national crisis , as Italy grappled with sovereign debt problems and Berlusconi faced criminal charges of tax fraud , for which he was subsequently convicted . He remains free pending an appeal . He was also embroiled in a scandal involving a young nightclub dancer - which led him to be charged with paying for sex with an underage prostitute .

He was replaced by Monti , a respected economist and former European Commissioner , who was invited by Italy 's President Giorgio Napolitano to lead a cabinet of unelected technocrats . Monti 's government implemented a program of tax rises and austerity measures in an attempt to resolve Italy 's economic crisis .

Who are the candidates ?

The election is a four-horse race between political coalitions led by Bersani , Berlusconi , Monti , and the anti-establishment movement led by ex-comedian Beppe Grillo . Polls are banned within two weeks of election day , but the most recent ones had Bersani holding onto a slender lead over Berlusconi , followed by Grillo in distant third .

READ MORE : Will Monte Paschi banking scandal throw open Italy 's election race ?

The center-left alliance is dominated by the Democratic Party , led by Bersani . He is a former Minister of Economic Development in Romano Prodi 's government from 2006-8 -- and has held a comfortable lead in polls , but that appears to be gradually being eroded by Berlusconi .

Italy 's political system encourages the forming of alliances , and the Democratic Party has teamed with the more left-wing Left Ecology Freedom party .

The 61-year-old Bersani comes across as `` bluff and homespun , and that 's part of his appeal -- or not , depending on your point of view , '' said political analyst James Walston , department chair of international relations at the American University of Rome .

He described Bersani , a former communist , as a `` revised apparatchik , '' saying the reform-minded socialist was paradoxically `` far more of a free marketeer than even people on the right . ''

Bersani has vowed to continue with Monti 's austerity measures and reforms , albeit with some adjustments , if he wins .

At second place in the polls is the center-right alliance led by Berlusconi 's PdL , in coalition with the right-wing , anti-immigration Northern League .

Berlusconi has given conflicting signals as to whether he is running for the premiership , indicating that he would seek the job if his coalition won , but contradicting that on other occasions .

In a recent speech , he proposed himself as Economy and Industry Minister , and the PdL Secretary Angelino Alfano as prime minister .

Roberto Maroni , leader of the Northern League , has said the possibility of Berlusconi becoming prime minister is explicitly ruled out by the electoral pact between the parties , but the former premier has repeatedly said he plays to win , and observers believe he is unlikely to pass up the chance to lead the country again if the opportunity presents itself .

Berlusconi has been campaigning as a Milan court weighs his appeal against a tax fraud conviction , for which he was sentenced to four years in jail last year . The verdict will be delivered after the elections ; however , under the Italian legal system , he is entitled to a further appeal in a higher court . Because the case dates to July 2006 , the statute of limitations will expire this year , meaning there is a good chance none of the defendants will serve any prison time .

He is also facing charges in the prostitution case -LRB- and that he tried to pull strings to get her out of jail when she was accused of theft -RRB- -- and in a third case stands accused of revealing confidential court information relating to an investigation into a bank scandal in 2005 .

Despite all this , he retains strong political support from his base .

`` Italy is a very forgiving society , it 's partly to do with Roman Catholicism , '' said Walston . `` There 's sort of a ` live and let live ' idea . ''

Monti , the country 's 69-year-old technocrat prime minister , who had never been a politician before he was appointed to lead the government , has entered the fray to lead a centrist coalition committed to continuing his reforms . The alliance includes Monti 's Civic Choice for Monti , the Christian Democrats and a smaller centre-right party , Future and Freedom for Italy .

As a `` senator for life , '' Monti is guaranteed a seat in the senate and does not need to run for election himself , but he is hitting the hustings on behalf of his party .

In a climate of widespread public disillusionment with politics , comedian and blogger Beppe Grillo is also making gains by capturing the protest vote with his Five Star Movement . Grillo has railed against big business and the corruption of Italy 's political establishment , and holds broadly euro-skeptical and pro-environmental positions .

How will the election be conducted ?

Italy has a bicameral legislature and a voting system which even many Italians say they find confusing .

Voters will be electing 315 members of the Senate , and 630 members of the Chamber of Deputies . Both houses hold the same powers , although the Senate is referred to as the upper house .

Under the country 's closed-list proportional representation system , each party submits ranked lists of its candidates , and is awarded seats according to the proportion of votes won -- provided it passes a minimum threshold of support .

Seats in the Chamber of Deputies are on a national basis , while seats in the senate are allocated on a regional one .

The party with the most votes are awarded a premium of bonus seats to give them a working majority .

The prime minister needs the support of both houses to govern .

Who is likely to be the next prime minister ?

On current polling , Bersani 's bloc looks the likely victor in the Chamber of Deputies . But even if he maintains his lead in polls , he could fall short of winning the Senate , because of the rules distributing seats in that house on a regional basis .

Crucial to victory in the Senate is winning the region of Lombardy , the industrial powerhouse of the north of Italy which generates a fifth of the country 's wealth and is a traditional support base for Berlusconi . Often compared to the U.S. state of Ohio for the `` kingmaker '' role it plays in elections , Lombardy has more Senate seats than any other region .

If no bloc succeeds in controlling both houses , the horse-trading begins in search of a broader coalition .

Walston said that a coalition government between the blocs led by Bersani and Monti seemed `` almost inevitable , '' barring something `` peculiar '' happening in the final stages of the election campaign .

Berlusconi , he predicted , would `` get enough votes to cause trouble . ''

What are the main issues ?

There 's only really one issue on the agenda at this election .

The eurozone 's third largest economy is hurting , with unemployment surpassing 11 % -- and hitting 37 % for young people .

Voters are weighing the question of whether to continue taking Monti 's bitter medicine of higher taxation and austerity measures , while a contentious property tax is also proving a subject of vexed debate .

Walston said the dilemma facing Italians was deciding between `` who 's going to look after the country better , or who 's going to look after my pocket better . ''

He said it appeared voters held far greater confidence in the ability of Monti and Bersani to fix the economy , while those swayed by appeals to their own finances may be more likely to support Berlusconi .

But he said it appeared that few undecided voters had any faith in Berlusconi 's ability to follow through on his pledges , including a recent promise to reverse the property tax .

What are the ramifications of the election for Europe and the wider world ?

Improving the fortunes of the world 's eighth largest economy is in the interests of Europe , and in turn the global economy .

Italy 's woes have alarmed foreign investors . However , financial commentator Nicholas Spiro , managing director of consultancy Spiro Sovereign Strategy , says the European Central Bank 's bond-buying program has gone a long way to mitigating investors ' concerns about the instability of Italian politics .

Why is political instability so endemic to Italy ?

Italy has had more than 60 governments since World War II -- in large part as a by-product of a system designed to prevent the rise of another dictator .

Parties can be formed and make their way on to the political main stage with relative ease -- as witnessed by the rise of Grillo 's Five Star Movement , the protest party which was formed in 2009 but in local and regional elections has even outshone Berlusoni 's party at times .

Others point to enduringly strong regional identities as part of the recipe for the country 's political fluidity .

READ MORE : Italian Elections 2013 : Fame di sapere -LRB- hunger for knowledge -RRB-

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Silvio Berlusconi is campaigning to win his old job back for the fourth time

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The eurozone 's third largest economy is hurting , with unemployment surpassing 11 %

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Pier Luigi Bersani of the center-left Democratic Party is expected to narrowly win

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Italy 's political system encourages the forming of alliances